This invention is directed to providing ventilation for a crawl space under a house or similar structure, and in particular to provide a fan system for the introduction of air into and from the crawl space as well as circulation within the crawl space to reduce the amount of moisture present in the crawl space.
The moisture content within a crawl space is the result of having a space between the ground and the floor that is subjected to a moisture buildup from various sources. Some of these sources include leaking pipes, condensation on the exterior surfaces of heating and air conditioning ducts and natural ground water intrusion into the crawl space. Very little opportunity exists for the moisture to be discharged from the crawl space. Openings in the exterior walls are generally small and not properly located to keep the moisture content of the crawl space air from reaching a high percentage. The need exists to provide a positive flow of the air not only within the crawl space but also from a source having a lower percentage of moisture introduced into the crawl space and discharging the air within the crawl space having a high percentage of moisture.
The lack of circulation or movement of air within a crawl space results in higher concentrations of radon gas and the inability of the air to carry moisture from the crawl space that has evaporated into the air from damp surfaces. The harmful effects of radon gas are well known in the building industry and special construction features are used to keep concentrations low, including a ground cover, vent pipes and crawl space vents. In addition, air moving across a moist surface will collect moisture from the surface by evaporation from the surface and transport this excess moisture in the air away from the surface. The better the air circulation the more moisture will be removed from the crawl space by evaporation. This moisture reducing effect is in addition to replacing air having a high percentage of moisture with air having a lower percent moisture as previously discussed.
Some of the bad effects of high moisture content in the crawl space air include wood rot, mold, mildew, fungi, bacteria growth and insect infestation, to mention a few. The crawl space air can have an odor which is also objectionable. Radon gas content of a crawl space having a high moisture content is generally found to be higher than that in a crawl space with a low moisture content. A lower moisture content air of a crawl space has many advantages including: helping prevent termite infestation; helping prevent rusting and corrosion of heating and air conditioning equipment; helping maintain floor insulation “R” factors; and helping prevent high moisture content air from reaching the living space in a home.
Typical crawl space ventilation systems have been disclosed in U.S. Pat. Nos. 3,368,756; 4,702,149; 4,829,882; and 4,877,182. The ventilator systems of '756 and '149 are passive systems where the air is not being forced through the crawl space and depends on the natural flow as a result of temperature differences. The ventilation systems of '182 and '882 depend on both intake and exhaust units at the exterior openings and vents of the crawl space. Numerous dehumidification systems are available in the industry to actively remove moisture from a space to reduce the moisture content of the air. These systems are generally used to condition the living area air and are not cost effective for use in conditioning air in a crawl space.
The need remains to have an efficient and cost effective ventilation system for the crawl space under the lower floor of a home or building not built on the ground. The ventilation system should be easy to install as an aftermarket device.
Accordingly, an object of the present invention is to provide a ventilation system for a home or building crawl space which is easily installed and operated but effective in reducing the moisture content of the air within the crawl space.
An additional object of the present invention is to provide air circulation within a crawl space that reduces the concentration of radon gas and helps reduce the moisture in the crawl space by removing moist air caused by evaporation from damp surfaces.
Another object of the present invention is to provide a high velocity and high cubic feet per minute ventilating system which is cost effective to produce, install and operate.
A further object of the present invention is to provide a control system which operates with limited changes and can be set to provide the low moisture content air for the crawl space.
Yet another object of the present invention is to provide a crawl space ventilation system that accounts for the relative humidity of the crawl space compared with the ambient air and the crawl space temperature.